Magnetism and Electric Motors (5/12/15)

The Inner Workings of Magnets

Drawn above are what the domains inside a non-magnetized (on the left) and magnetized piece of metal look like. The reason something is not magnetized is because the domains are all random and not aligned perfectly. We had to come up with some ideas of how to demagnetize an object based on what we learned. Shown below are our answers, as well as the demonstration of demagnetization.

Above, a paper clip was magnetized and then heated up, and ended up losing its magnetism.

Electric Motor

Our electric motor.

Our motor in action!

In regards to the electric motor, we were asked to answer the questions above.

Our original setup is on the left, and the switched poles one is on the right, shown above. After following the instructions above, the answer to the questions are as follows:

1) When powered on, the motor turned counterclockwise.

2) When the current was switched, the motor turned clockwise.

Explain: The reason for this is because the motor rotation follows the flow of the current. Since the current changed directions, the motor also change directions.

3) The motor turned counterclockwise when the poles were switched.
Explain: The reasoning for this is that switching the poles changes the direction of the magnetic field, so the direction of torque changes as well. The motor was basically brought back to its original starting position due to the two changes that occurred.

Our answer to how the motors may go bad over time.

At the end of this activity, we had to create our own motor by making a coil of wire, which had two leads attached in order to cause a flow of current to pass through. By placed a magnet under it, we introduced a magnetic field, and the coil was able to spin rapidly. Essentially, it is the culmination of everything we have learned being put into practice.

The Magnetic Field Near a Current-Carrying Wire

The pole in the center acts as our wire in this situation. There is no current flowing through it, so all the compasses are pointing north at the moment.  

Our prediction (above) is that once there is a current flowing, the compasses will point in a circular motion around the wire.

As shown above, the compasses do end up pointing in a circular direction once a current is passed through the wire. This means that the magnetic field is traveling in a circle around a wire when current is flowing.

Summary:

In summation we now know why some objects are magnetized, while others are not. We also did an extensive analysis on motors and exactly how they are powered by both magnetism and electricity.  This allowed us to build a small skeleton of a motor using current and a magnet. We also visually understand just how a magnetic field is flowing around a current carrying wire. It travels in a circular motion, and is most likely affected by the direction of the current as well.